People involved at OAB: Bellazzini, Cacciari, Fusi Pecci, Origlia, Pancino
Stellar evolutionary models are often used to derive relevant properties of globular star clusters (GCs) and galaxies, such as their age and metal content. The Luminosity Function of the stellar sequences in the CMDs, from the Main Sequence Turn Off (MS-TO) up to the termination of the Asymptotic Giant Branch (AGB), has been recognized as the most powerful tool for testing stellar evolutionary models (with particular regard to the accuracy of the input physics, the reliability of canonical assumptions, etc.).
A fully fruitful test requires that the observations be a) complete, b) statistically significant, and c) accurate and adequate for each specific evolutionary sequence. Point (a) means that virtually all of the stars in a given area of the cluster are measured down to a given magnitude level, and that reliable corrections for incompleteness can be applied below that level. Point (b) means that observations should cover most of the cluster extension. Point (c) requires infrared observations to measure the cool Red Giant Branch (RGB) stars and UV observations to properly study the blue sequences such as the Horizontal Branch and the Blue Stragglers.